[X,Y] = meshgrid(-3:.50:3);
Z = peaks(X,Y);
[XI,YI] = meshgrid(-3:.150:3);
ZZ = interp2(X,Y,Z,XI,YI);
surfl(X,Y,Z);hold on;
surfl(XI,YI,ZZ+15)
axis([-3 3 -3 3 -5 20]);shading flat
hold off
